Last year was the warmest on record in the lower 48 states and had some of the most extreme weather events ever recorded, the National Oceanic and Atmospheric Administration said today.

The average temperature for the lower 48 states last year was 55.3 degrees Fahrenheit, 3.2 degrees above the 20th-century average and 1 degree higher than the previous warmest year recorded, NOAA said in its annual "State of the Climate" report.

That 1 degree is a significant uptick when looking at 117 years of temperature data, NOAA scientists said. Previously there was a difference of 4 F between the average of the previous warmest year, 1998, and the coldest year, 1917.

"The difference between the record coldest and the previous record warmest year in 117 years of data was encompassed in 4 degrees. Now, 2012 is 1 degree outside that envelope. We're taking quite a large step," said Jake Crouch, a climate scientist at NOAA's National Climatic Data Center.

The year also saw the second most extreme weather on record, with high temperatures, drought, tornadoes and a superstorm that hit the Northeast. In total, there were 11 weather disasters that caused more than $1 billion in losses, NOAA says.

Worldwide, 2012 did not have the hottest average temperatures across the globe. NOAA will address global average temperatures in a separate report, to be released next week. NOAA scientists said that they are still crunching data for December but that temperatures through November ranked 2012 as the eighth-warmest year on record for worldwide averages.

The agency scores weather events for a "climate extremes index." This year's total was nearly twice the average and second only to 1998, which had a slightly higher score due to increased landfall in tropical cyclones.

Both climate change and local and regional weather variability likely played a role in the higher temperatures and extreme weather events, NOAA scientists said. Last year's weather falls in line with what scientists expect to see from climate change, although one year of cold or warm weather cannot prove or disprove global warming.

"The heat we saw in the U.S. and the weather and climate data in the U.S. is consistent with what we would expect to see in a warming world," said Deke Arndt, chief of the climate monitoring branch for NOAA's National Climatic Data Center. "But itself, it doesn't prove or disprove anything but it is a data point in a long series of data points that helps us understand what is going on and what we may see in the future."

Advocacy groups are already pointing to the new report to call for government action on climate change.

"Unfortunately, this won't be the last time we break records like this," Angela Anderson of the Union of Concerned Scientists said in a statement today. "The longer we delay reducing emissions, the more climate change we're going to lock in. The president has promised to make climate change a priority in his second term, but he needs to turn those words into action."